Abstracts

Rationale: Epilepsy affects 1 % of the population and ~30% are medically intractable. (PNES) psychogenic nonepileptic events are commonly seen at epilepsy centers and are believed to represent 10-20 % of all referrals. Other common monitoring outcomes for non epileptic seizures include behavioral spells of uncertain etiology, neurocardiogenic syncope, cardiac arrhythmias, breath holding spells and movement disorders. The prevalence of PNES in general population is unknown. Past studies suggest the prevalence of PNES varies between 1/50,000 and 1/3000 (Seizure 2000; 9:280-281). The main goal of this study was to estimate the prevalence of psychogenic epilepsy in a unique population area (i.e., one with a single epilepsy monitoring center; New Mexico). In addition, we examined the eventual disposition of all patients who underwent V-EEG monitoring and the presence or absence of interictal EEG abnormalities in patients with PNES. Methods: Methods: Retrospective study of V-EEG reports of 934 patients who were admitted for monitoring for more than 20 hours with concomitant ECG at University of New Mexico Hospital with a diagnosis of possible seizures. For prevalence of PNES we used the following generally accepted estimates used in other publications; prevalence of epilepsy 0.5-1% and proportion of intractable epilepsy 20-30%, and population statistics for the state of New Mexico. Results: In total, 934 inpatients V-EEG monitoring sessions were performed. PNES were diagnosed in 15.41% (144 patients), epilepsy in 30.72% (287), both (PNES +E) 0.85% (8). No event occurred in 24.73% (231), undiagnosed behavioral events consisting of brief staring with unresponsiveness 9.63% (90), undiagnosed other behavioral events 13.49% (126), other diagnosed but non epileptic events 5.13% (48). Using the low estimates of epilepsy prevalence and intractability, and assuming that all intractable patients would undergo epilepsy monitoring, PNES in New Mexico would be 22.5/100,000. Using the higher estimates, prevalence of PNES in New Mexico would be 45/100,000. Retrospective review of V-EEG reports in patients with PNES showed interictal epileptiform activity was found in 13.88% (20), non specific abnormalities in 20.13% (29) and normal in 65.9%(95). Conclusions: In comparison to previous studies examining the prevalence of PNES alone, our study shows a much higher prevalence. Although a small proportion of patients in the New Mexico area are referred elsewhere for monitoring, adjusting for that group should make our estimate of prevalence higher. Our study therefore suggests that prior estimates of the prevalence of PNES may be much lower than the actual prevalence.